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Homework Help: OCHEM - Linear Combination of Atomic Orbitals

  1. Sep 20, 2008 #1
    1. The problem statement, all variables and given/known data
    Draw an LCAO representation of all of the bonding orbitals for C2H2O. Be sure to clearly state the hybridization of the two carbons and the oxygen in addition to drawing the orbital representation. Also show clearly what orbital any unshared pairs occupy.

    2. Relevant equations

    3. The attempt at a solution
    I started out by drawing the molecular structure and came up with CH2=C=O where the 1st carbon has an sp2 hybridization, the 2nd carbon has an sp hybridization, and the oxygen has an sp2 hybridization.

    I don't know where to go from here. I have seen LCAO representations but they have only been single bonds between two hydrogen atoms like the one on this site http://www.science.uwaterloo.ca/~cchieh/cact/fig/sigmah2.gif

    How would I go about forming a Linear Combination of Atomic Orbitals with double bonds between the carbon-carbon and carbon-oxygen bonds, as well as the lone pairs?

    Thank you!
  2. jcsd
  3. Sep 21, 2008 #2
    The first thing to do is recognize which is higher in energy, sigma or pi orbitals? Remember than sigma occurs with head on overlap while pi occurs with parallel overlap. Next is recognizing which is higher in energy, C=O or C=C. Also remember than for every atomic orbital you use, you get one molecular orbital, bonding and anti-bonding. Which is higher in energy, bonding or anti-bonding orbitals?
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